1. Field of the Invention
The subject invention relates to a thermosiphon cooling assembly for cooling an electronic device.
2. Description of the Prior Art
The operating speed of computers is constantly being improved to create faster and faster computers. With this, comes increased heat generation and a need to effectively dissipate that heat.
Heat exchangers and heat sink assemblies have been used that apply natural or forced convection cooling methods to dissipate heat from electronic devices that are highly concentrated heat sources such as microprocessors and computer chips. These heat exchangers typically use air to directly remove heat from the electronic devices; however air has a relatively low heat capacity. Thus, liquid-cooled units called LCUs employing a cold plate in conjunction with high heat capacity fluids have been used to remove heat from these types of heat sources. Although LCUs are satisfactory for moderate heat flux, increasing computing speeds have required more effective heat sink assemblies.
Accordingly, thermosiphon cooling units (TCUs) have been used for cooling electronic devices having a high heat flux. A typical TCU absorbs heat generated by the electronic device by vaporizing the working fluid housed on the boiler plate of the unit. The boiling of the working fluid constitutes a phase change from liquid-to-vapor state and as such the working fluid of the TCU is considered to be a two-phase fluid. The vapor generated during boiling of the working fluid is then transferred to a condensing tube, where it is liquefied by the process of film condensation over the condensing surface of the TCU. The heat is rejected into a stream of air flowing through a tube running through the condensing tube or flowing over fins extending from the condensing tube. The condensed liquid is returned back to the boiler plate by gravity to continue the boiling-condensing cycle.
Examples of cooling systems for electronic devices are disclosed in U.S. Pat. No. 6,867,974 to Luo; U.S. Pat. No. 6,986,384 to Wagner et al.; and U.S. Pat. No. 6,840,311 to Ghosh et al.
The Luo patent discloses an assembly for cooling an electronic device having an evaporating unit housing a liquid refrigerant connected to a condensing tube where the condensing tube may resemble a truncated cone having a cross section that is gradually reduced in a direction away from the evaporating unit. Vapor produced by boiling the refrigerant gathers in the condensing tube and the heat contained within the vapor is transferred to cooling fins attached to the exterior of the condensing tube.
The Wagner et al. patent discloses an assembly for cooling an electronic device having an air moving device mounted directly to the cooling assembly to move air across the cooling assembly on a central axis perpendicular to the assembly. The Ghosh et al. patent discloses an assembly for cooling an electronic device having an evaporating unit, a condensing tube, and internal condensing fins located within the condensing tube. The condensing fins transfer heat contained within vapor boiled off a liquid refrigerant to the exterior of the assembly.
Although the prior art dissipates heat from electronic devices, as computing speeds increase, there is a continuing need for alternative cooling devices having more efficient heat transfer capabilities.